PS/2 Mouse: Difference between revisions
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{| class="wikitable" |
{| class="wikitable" |
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! colspan=" |
! colspan="3" | Standard PS/2 Mouse Commands |
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! Byte !! Description |
! Byte !! Data byte !! Description |
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| 0xE6 || None || Set Scaling 1:1 |
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| 0xFF || Reset |
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| 0xE7 || None || Set Scaling 2:1 |
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| 0xFE || Resend |
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| 0xE8 |
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| 0xF6 || Set Defaults |
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{| {{wikitable}} |
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! Byte |
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! Resolution |
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| 00 |
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| 1 count/mm |
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| 01 |
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| 2 count/mm |
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| 02 |
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| 4 count/mm |
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| 03 |
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| 8 count/mm |
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|} |
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| Set Resolution |
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| 0xE9 || None || Status Request |
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| 0xEA || None || Set Stream Mode |
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| 0xF4 || Enable Data Reporting |
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| 0xEB || None || Read Data |
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| 0xEC || None || Reset Wrap Mode |
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| 0xEE || None || Set Wrap Mode |
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| 0xF0 || None || Set Remote Mode |
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| 0xF2 |
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| 0xEC || Reset Wrap Mode |
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| None |
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| Get Device ID. See [["8042" PS/2 Controller#Detecting PS/2 Device Types|Detecting PS/2 Device Types]] for the response bytes. |
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| 0xF3 |
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| 0xEB || Read Data |
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| Sample rate |
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| Set Sample Rate, valid values are 10, 20, 40, 60, 80, 100, and 200. |
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| 0xF4 || None || Enable Data Reporting |
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| 0xF5 || None || Disable Data Reporting |
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| 0xE9 || Status Request |
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| 0xF6 || None || Set Defaults |
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| 0xFE || None || Resend |
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| 0xFF || None || Reset ('''Note: After the result of the power-on test is sent, the mouse sends its ID (0x00)''') |
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|} |
|} |
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The most command reply is ''0xFA'' from the master (mouse), which means acknowledge. You may then get a variable number of bytes afterwards depending on the command. You may also receive other command replies which may state that the master (mouse) has encountered an error decoding your command. For a more detailed list check out some of the links above or look through the Linux source tree. |
The most common command reply is ''0xFA'' from the master (mouse), which means acknowledge. You may then get a variable number of bytes afterwards depending on the command. You may also receive other command replies which may state that the master (mouse) has encountered an error decoding your command. For a more detailed list check out some of the links above or look through the Linux source tree. |
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First, you have to enable the mouse on the PS/2 bus. This requires sending one byte which is clocked over the PS/2 interface. You will then get a response regarding the result. By sending ''0xF4'' (Enable Data Reporting) the mouse should reply back with a ''0xFA'' which means acknowledgement. Then afterwards as the mouse pointer is moved it will send back the generic packet format like below. Unless |
First, you have to enable the mouse on the PS/2 bus. This requires sending one byte which is clocked over the PS/2 interface. You will then get a response regarding the result. By sending ''0xF4'' (Enable Data Reporting) the mouse should reply back with a ''0xFA'' which means acknowledgement. Then afterwards as the mouse pointer is moved it will send back the generic packet format like below. Unless you enable an enhanced mode for the mouse (non-standard) this is what you will get when ever the mouse is moved. |
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{| class="wikitable" |
{| class="wikitable" |
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! BYTE!!7!!6!!5!!4!!3!!2!!1!!0 |
! BYTE!!7!!6!!5!!4!!3!!2!!1!!0 |
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|- align="center" |
|- align="center" |
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| 0 || yo || xo || ys || xs || |
| 0 || yo || xo || ys || xs || 1 || bm || br || bl |
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|- align="center" |
|- align="center" |
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| 1 || colspan="8" | |
| 1 || colspan="8" | X-Axis Movement Value |
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|- align="center" |
|- align="center" |
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| 2 || colspan="8" | |
| 2 || colspan="8" | Y-Axis Movement Value |
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|} |
|} |
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{| class="wikitable" |
{| class="wikitable" |
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| xs || X-Axis Sign Bit (9-Bit X-Axis Relative Offset) |
| xs || X-Axis Sign Bit (9-Bit X-Axis Relative Offset) |
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| 1 || Always One |
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| bm || Button Middle (Normally Off = 0) |
| bm || Button Middle (Normally Off = 0) |
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| bl || Button Left (Normally Off = 0) |
| bl || Button Left (Normally Off = 0) |
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| xm || X-Axis Movement Value |
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|- |
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| ym || Y-Axis Movement Value |
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|} |
|} |
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Each X and Y axis value is relative. The mouse device does not track |
Each X and Y axis value is relative. The mouse device does not track its location in absolute coordinates. This should also be apparent by the 9-bit values. Instead, it sends back saying I moved this far to the left, to the right, down, or up. To keep track of a mouse position you need to accumulate these relative offsets into a absolute position offset in your code: |
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<pre> |
<pre> |
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mouse_x = mouse_x + mouse_packet_rel_x |
mouse_x = mouse_x + mouse_packet_rel_x |
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''Being these 9-bit values are signed the above pseudo would work.'' |
''Being these 9-bit values are signed the above pseudo would work.'' |
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Also, if you simply read the |
Also, if you simply read the X- or Y-Axis Movement Value fields you will get an 8-bit unsigned value. Which, if used as unsigned will yield incorrect behavior. If you convert it into a signed 8-bit value you will get behavior that is similar to correct, but strange artifacts will appear when the mouse is moved fast. The correct way to produce a 9-bit or greater signed value is as follows: |
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<pre> |
<pre> |
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state = first_byte |
state = first_byte |
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rel_y = d - ((state << 3) & 0x100) |
rel_y = d - ((state << 3) & 0x100) |
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</pre> |
</pre> |
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The pseudo code above will cause ''((state << 4) & 0x100)'' to equal ''0x100'' only if the signed bit (9'th bit stored in the first byte) is set. If the 9'th bit is set then the value is deemed negative, but the value in ''second_byte'' is not stored in one or two's complement form. It is instead stored as a positive 8-bit value. So, if ''second_byte'' is say a ''2'' then it will become ''2 minus 0'' since the negative (9'th bit) is off. But, if it is on then it will become ''2 minus 0x100'' which will produce the twos complement, or ''-2''. It will also cause the register to be correctly sign extended no matter |
The pseudo code above will cause ''((state << 4) & 0x100)'' to equal ''0x100'' only if the signed bit (9'th bit stored in the first byte) is set. If the 9'th bit is set then the value is deemed negative, but the value in ''second_byte'' is not stored in one or two's complement form. It is instead stored as a positive 8-bit value. So, if ''second_byte'' is say a ''2'' then it will become ''2 minus 0'' since the negative (9'th bit) is off. But, if it is on then it will become ''2 minus 0x100'' which will produce the twos complement, or ''-2''. It will also cause the register to be correctly sign extended no matter its size. |
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=== Set Sample Rate Example === |
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To set the sample rate for example, which is a command with a data byte, one would need to do: |
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<syntaxhighlight lang="c"> |
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outb(0xD4, 0x64); // tell the controller to address the mouse |
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outb(0xF3, 0x60); // write the mouse command code to the controller's data port |
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while(!(inb(0x64) & 1) asm("pause"); // wait until we can read |
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ack = inb(0x60); // read back acknowledge. This should be 0xFA |
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outb(0xD4, 0x64); // tell the controller to address the mouse |
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outb(100, 0x60); // write the parameter to the controller's data port |
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while(!(inb(0x64) & 1) asm("pause"); // wait until we can read |
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ack = inb(0x60); // read back acknowledge. This should be 0xFA |
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</syntaxhighlight> |
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== Mouse Extensions == |
== Mouse Extensions == |
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compatibility mode described above. |
compatibility mode described above. |
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=== Z-axis === |
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To enable the Intellimouse Z-axis extension, you have to set some magic into the sample rate: |
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<syntaxhighlight lang="c"> |
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set_mouse_rate(200); // see the example above |
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set_mouse_rate(100); |
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set_mouse_rate(80); |
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mouseid = identify(); // see Get Device ID, 0xF2 |
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</syntaxhighlight> |
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After that the mouse should not return Mouse ID ''0'', but ''3'', and will send 4 bytes data packages as follows: |
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{| class="wikitable" |
{| class="wikitable" |
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! colspan="9" | |
! colspan="9" | Intellimouse #1 PS/2 Mouse Packet Bits |
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! BYTE!!7!!6!!5!!4!!3!!2!!1!!0 |
! BYTE!!7!!6!!5!!4!!3!!2!!1!!0 |
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|- align="center" |
|- align="center" |
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| 0 || yo || xo || ys || xs || 1 || bm || br || bl |
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|- align="center" |
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|} |
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| 1 || colspan="8" | X-Axis Movement Value |
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|- align="center" |
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| 2 || colspan="8" | Y-Axis Movement Value |
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|- align="center" |
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| 3 || colspan="8" | Z-Axis Movement Value |
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|} |
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The Z-axis Movement Value is in "2's complement" format. Valid values are -8 to +7. Other bytes are identical to the PS/2 packet. |
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=== 5 buttons === |
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To enable the 4th and 5th buttons, first you have to try to enable Z-axis, and you can only follow with this if the identification returned ''3''. |
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<syntaxhighlight lang="c"> |
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if(mouseid == 3) { |
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set_mouse_rate(200); |
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set_mouse_rate(200); |
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set_mouse_rate(80); |
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mouseid = identify(); |
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} |
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</syntaxhighlight> |
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If this was successful, the identify command should now return Mouse ID ''4'', and the 4 bytes packets will look like this: |
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{| class="wikitable" |
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! colspan="9" | Intellimouse #2 PS/2 Mouse Packet Bits |
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|- |
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! BYTE!!7!!6!!5!!4!!3!!2!!1!!0 |
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|- align="center" |
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| 0 || yo || xo || ys || xs || 1 || bm || br || bl |
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|- align="center" |
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| 1 || colspan="8" | X-Axis Movement Value |
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|- align="center" |
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| 2 || colspan="8" | Y-Axis Movement Value |
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|- align="center" |
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| 3 || 0 || 0 || b5 || b4 || colspan="4" | Z-Axis Movement Value |
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|} |
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Here the X-Axis Movement Value is stored only on the low 4 bits and the last byte is not sign extended. Bits 4 and 5 represents the pressed status of buttons 4 and 5 in that order, same as with bm, br and bl. |
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=== Emulation === |
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Normally bochs does only emulate generic PS/2 mouse. To make bochs to handle Z-axis, you should set the proper mouse type in your bochrc file: |
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<pre> |
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mouse: type=imps2, enabled=1 |
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</pre> |
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If you did the sample rate magic right, then you should see this on the bochs console as soon as you issue the last set sample rate command: |
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<pre> |
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0000000000i[KBD ] wheel mouse mode enabled |
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</pre> |
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Qemu on the other hand understands not only the Z-axis mode, but the 5 buttons mode too, and returns Mouse ID ''4'' if you did everything right. |
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==See Also== |
==See Also== |
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===External Links=== |
===External Links=== |
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*[http://www.computer-engineering.org/ps2mouse/ www.Computer-Engineering.org/ps2mouse] |
*[http://www.computer-engineering.org/ps2mouse/ www.Computer-Engineering.org/ps2mouse] |
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*[http://users.utcluj.ro/~baruch/sie/labor/PS2/PS-2_Mouse_Interface.htm users.utcluj.ro/~baruch/sie/labor/PS2/PS-2_Mouse_Interface.htm] |
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=== Implementations === |
=== Implementations === |
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* [http://lxr.linux.no/#linux+v3.5.4/drivers/input/mouse/psmouse-base.c Linux] (C,GPL) |
* [http://lxr.linux.no/#linux+v3.5.4/drivers/input/mouse/psmouse-base.c Linux] (C,GPL) |
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[[Category:Human Interface Device]] |
[[Category:Human Interface Device]] |
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[[Category:Common Devices]] |
[[Category:Common Devices]] |
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[[Category:Hardware Interfaces]] |
Latest revision as of 04:45, 9 June 2024
Also be sure to read Mouse Input.
Overview
The PS/2 Mouse is a device that talks to a PS/2 controller using serial communication. Ideally, each different type of PS/2 controller driver should provide some sort of standard/simple "send byte/receive byte" interface, and the PS/2 Mouse driver would use this interface without caring about lower level details (like what type of PS/2 controller the device is plugged into).
Mouse Device Over PS/2
Here is the table of command a generic PS/2 compatible mouse understands:
Standard PS/2 Mouse Commands | ||||||||||||
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Byte | Data byte | Description | ||||||||||
0xE6 | None | Set Scaling 1:1 | ||||||||||
0xE7 | None | Set Scaling 2:1 | ||||||||||
0xE8 |
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Set Resolution | ||||||||||
0xE9 | None | Status Request | ||||||||||
0xEA | None | Set Stream Mode | ||||||||||
0xEB | None | Read Data | ||||||||||
0xEC | None | Reset Wrap Mode | ||||||||||
0xEE | None | Set Wrap Mode | ||||||||||
0xF0 | None | Set Remote Mode | ||||||||||
0xF2 | None | Get Device ID. See Detecting PS/2 Device Types for the response bytes. | ||||||||||
0xF3 | Sample rate | Set Sample Rate, valid values are 10, 20, 40, 60, 80, 100, and 200. | ||||||||||
0xF4 | None | Enable Data Reporting | ||||||||||
0xF5 | None | Disable Data Reporting | ||||||||||
0xF6 | None | Set Defaults | ||||||||||
0xFE | None | Resend | ||||||||||
0xFF | None | Reset (Note: After the result of the power-on test is sent, the mouse sends its ID (0x00)) |
The most common command reply is 0xFA from the master (mouse), which means acknowledge. You may then get a variable number of bytes afterwards depending on the command. You may also receive other command replies which may state that the master (mouse) has encountered an error decoding your command. For a more detailed list check out some of the links above or look through the Linux source tree.
First, you have to enable the mouse on the PS/2 bus. This requires sending one byte which is clocked over the PS/2 interface. You will then get a response regarding the result. By sending 0xF4 (Enable Data Reporting) the mouse should reply back with a 0xFA which means acknowledgement. Then afterwards as the mouse pointer is moved it will send back the generic packet format like below. Unless you enable an enhanced mode for the mouse (non-standard) this is what you will get when ever the mouse is moved.
Generic PS/2 Mouse Packet Bits | ||||||||
---|---|---|---|---|---|---|---|---|
BYTE | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
0 | yo | xo | ys | xs | 1 | bm | br | bl |
1 | X-Axis Movement Value | |||||||
2 | Y-Axis Movement Value |
Code | Description |
---|---|
yo | Y-Axis Overflow |
xo | X-Axis Overflow |
ys | Y-Axis Sign Bit (9-Bit Y-Axis Relative Offset) |
xs | X-Axis Sign Bit (9-Bit X-Axis Relative Offset) |
1 | Always One |
bm | Button Middle (Normally Off = 0) |
br | Button Right (Normally Off = 0) |
bl | Button Left (Normally Off = 0) |
Each X and Y axis value is relative. The mouse device does not track its location in absolute coordinates. This should also be apparent by the 9-bit values. Instead, it sends back saying I moved this far to the left, to the right, down, or up. To keep track of a mouse position you need to accumulate these relative offsets into a absolute position offset in your code:
mouse_x = mouse_x + mouse_packet_rel_x mouse_y = mouse_y + mouse_packet_rel_y
Being these 9-bit values are signed the above pseudo would work.
Also, if you simply read the X- or Y-Axis Movement Value fields you will get an 8-bit unsigned value. Which, if used as unsigned will yield incorrect behavior. If you convert it into a signed 8-bit value you will get behavior that is similar to correct, but strange artifacts will appear when the mouse is moved fast. The correct way to produce a 9-bit or greater signed value is as follows:
state = first_byte d = second_byte rel_x = d - ((state << 4) & 0x100) d = third_byte rel_y = d - ((state << 3) & 0x100)
The pseudo code above will cause ((state << 4) & 0x100) to equal 0x100 only if the signed bit (9'th bit stored in the first byte) is set. If the 9'th bit is set then the value is deemed negative, but the value in second_byte is not stored in one or two's complement form. It is instead stored as a positive 8-bit value. So, if second_byte is say a 2 then it will become 2 minus 0 since the negative (9'th bit) is off. But, if it is on then it will become 2 minus 0x100 which will produce the twos complement, or -2. It will also cause the register to be correctly sign extended no matter its size.
Set Sample Rate Example
To set the sample rate for example, which is a command with a data byte, one would need to do:
outb(0xD4, 0x64); // tell the controller to address the mouse
outb(0xF3, 0x60); // write the mouse command code to the controller's data port
while(!(inb(0x64) & 1) asm("pause"); // wait until we can read
ack = inb(0x60); // read back acknowledge. This should be 0xFA
outb(0xD4, 0x64); // tell the controller to address the mouse
outb(100, 0x60); // write the parameter to the controller's data port
while(!(inb(0x64) & 1) asm("pause"); // wait until we can read
ack = inb(0x60); // read back acknowledge. This should be 0xFA
Mouse Extensions
Here, an example of mouse that supports extensions. To maintain backwards compatibility you should have to activate these features through the PS/2 bus. Various mouse devices use different ways. Linux mouse drivers for example sometimes handle multiple different devices which all share the same standard packet format above, or at least support the compatibility mode described above.
Z-axis
To enable the Intellimouse Z-axis extension, you have to set some magic into the sample rate:
set_mouse_rate(200); // see the example above
set_mouse_rate(100);
set_mouse_rate(80);
mouseid = identify(); // see Get Device ID, 0xF2
After that the mouse should not return Mouse ID 0, but 3, and will send 4 bytes data packages as follows:
Intellimouse #1 PS/2 Mouse Packet Bits | ||||||||
---|---|---|---|---|---|---|---|---|
BYTE | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
0 | yo | xo | ys | xs | 1 | bm | br | bl |
1 | X-Axis Movement Value | |||||||
2 | Y-Axis Movement Value | |||||||
3 | Z-Axis Movement Value |
The Z-axis Movement Value is in "2's complement" format. Valid values are -8 to +7. Other bytes are identical to the PS/2 packet.
5 buttons
To enable the 4th and 5th buttons, first you have to try to enable Z-axis, and you can only follow with this if the identification returned 3.
if(mouseid == 3) {
set_mouse_rate(200);
set_mouse_rate(200);
set_mouse_rate(80);
mouseid = identify();
}
If this was successful, the identify command should now return Mouse ID 4, and the 4 bytes packets will look like this:
Intellimouse #2 PS/2 Mouse Packet Bits | ||||||||
---|---|---|---|---|---|---|---|---|
BYTE | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
0 | yo | xo | ys | xs | 1 | bm | br | bl |
1 | X-Axis Movement Value | |||||||
2 | Y-Axis Movement Value | |||||||
3 | 0 | 0 | b5 | b4 | Z-Axis Movement Value |
Here the X-Axis Movement Value is stored only on the low 4 bits and the last byte is not sign extended. Bits 4 and 5 represents the pressed status of buttons 4 and 5 in that order, same as with bm, br and bl.
Emulation
Normally bochs does only emulate generic PS/2 mouse. To make bochs to handle Z-axis, you should set the proper mouse type in your bochrc file:
mouse: type=imps2, enabled=1
If you did the sample rate magic right, then you should see this on the bochs console as soon as you issue the last set sample rate command:
0000000000i[KBD ] wheel mouse mode enabled
Qemu on the other hand understands not only the Z-axis mode, but the 5 buttons mode too, and returns Mouse ID 4 if you did everything right.
See Also
Articles
External Links
- www.Computer-Engineering.org/ps2mouse
- users.utcluj.ro/~baruch/sie/labor/PS2/PS-2_Mouse_Interface.htm
Implementations
- Linux (C,GPL)